/J  /?.  V.'  i 


B,  P.  1      i  'i  fust  5,  l'.KW. 

United  States  Department  of  Agriculture, 

BUREAU  OF  PLANT  INDUSTRY— Circular  No.  38. 

B.  T.  GALLOWAY.  Chief  of  Bureau. 


ROPEAN  CI  RRANT  RUST  ON  THE  \ 

AMERICA. 

By  1'kui.kv  Spaulding, 
Pathologist,  Offict  of  Investigations  in  'Forest  Pa 


INTRODUCTION. 


During  the  past  decade  an  intelligent  appreciation  of  forestry  meth- 
ods has  been  developed  in  this  country.  This  lias  produced  in  the 
Northeastern  and  North-Central  States  an  increasingly  insistent  demand 
tor  young  trees  suitable  for  the  purposes  of  reforestation  at  a  reasonable 
price.  A  large  import  trade  has  therefore  developed.  The  white  pine 
[Pinus  strobus  I..)  has  been  the  principal  timber  tree  of  the  section 
above  mentioned,  and  very  naturally  it  has  become  the  principal  species 
used  in  reforestation.  Hence,  the  import  trade  is  largely  concerned  with 
this  single  species,  and  white-pine  trees  are  now  coming  into  the  country 
at  the  rate  of  several  millions  a  year.  This  is  taking  place  with  abso- 
lutely no  inspection  regulations  other  than  local  ones,  which  are  utterly 
inadequate  to  deal  with  the  problem. 

American  plant  pathologists  have  been  anticipating  the  introduction 
of  the  European  blister  rust  I  Peridermium  strobi  Klebahn)  on  the  white 
pine. 

On  June  5,  1909,  Mr.  C.  R.  Pettis.  New  York  State  Forester,  asked 
the  writer  to  examine  some  three-year-old  seedlings  which  were  imported 
this  spring  from  Germany.  No  fruiting  bodies  were  found  present  on 
these  trees;  but  a  Foreman  who  had  planted  others  of  the  same  lot 
observed  thai  some  were  apparently  diseased  and  gave  so  good  a 
description  that  the  writer  was  convinced  that  Peridermium  strobi 
had  actually  been  imported  OD  the  trees.  A  personal  examination  on 
June 8  of  Borne  three-year-old  trees  which  had  been  imported  in  1908 
resulted   in   the  discovery  of   fruiting  bodies  of   the  fungus.     Further 

search    has    Bhown    that    the    disease   is    present.    BO    far   as   now    known. 

only  in   trees  from  J.   Heins   >"hne,  of  Halstenbek,  Germany.      Fur- 
thermore,  it    has    thus   far    been    found    only   in    trees    which    are  now 

- 


2  EUROPEAN    CURRANT    RUST    ON   WHITE   PINE. 

three  years  old,  i.  e.,  of  the  seeding  of  1906.  But  trees  from  this 
nursery  have  been  distributed  throughout  the  Northeastern  States  and 
Ontario.  Trees  of  the  same  age  from  other  European  nurseries  have 
been  examined,  but  none  of  the  disease  has  yet  been  found  in  them. 
It  is  apparent,  then,  that  a  very  severe  and  general  infection  of  the  white- 
pine  seedlings  took  place  in  this  nursery  in  the  year  1907.  This  con- 
clusion results  from  the  two  facts  (1)  that  the  fruiting  bodies  are  situ- 
ated on  the  wood  formed  in  the  second  year  and  (2)  that  the  fungus  is 
known  to  incubate  for  at  least  a  full  year  on  white  pine  before  fruiting. 
Because  of  the  general  distribution  of  the  disease  in  Europe  all  imported 
white-pine  trees  must  be  under  suspicion  until  proved  free  of  this  fungus. 

LIFE  HISTORY  OF  THE  FUNGUS. 

The  fungus  Peridermium  strobi  Klebahn  was  at  first  thought  to  be  a 
distinct  species,  but  has  subsequently  been  proved  to  be  one  stage  of 
the  blister  rust  of  currants  and  gooseberries  known  as  Cronartium 
ribicola  Fisch.  de  Waldh.a 

The  life  history  of  the  fungus  is  as  follows :  Spores  from  an  infested 
currant  or  gooseberry  bush  are  blown  to  some  neighboring  white-pine 
tree.  There  they  germinate  and  attack  the  bark  of  young  stems  and 
branches.  The  mycelium  vegetates  in  the  soft  inner  bark  until  the 
second  spring  after  infection  took  place.  Early  in  the  second  spring 
the  diseased  bark  becomes  thickened  and  the  stem  of  the  young  tree 
becomes  swollen  at  the  infected  place  for  a  length  of  one  to  several 
inches.  In  Germany  the  fruiting  bodies  break  through  the  bark  from 
April  20  to  June  1.  The  fruiting  bodies  at  first  are  light  orange  in 
color,  rounded  more  or  less,  and  project  from  the  surface  of  the  bark 
from  one- eighth  to  one-fourth  of  an  inch.  Later  they  break  open  irreg- 
ularly and  the  spores  are  scattered  by  the  wind.  After  the  spores  are 
scattered  there  is  left  a  whitish  membrane  which  is  very  fragile  and 
which  also  is  soon  blown  away  or  washed  off  by  rain.  This  leaves  only 
the  empty  fissures  in  the  bark  through  which  the  fruiting  bodies  extruded 
as  evidence  of  the  presence  of  the  fungus.  These  fissures  are  very  char- 
acteristic to  one  who  is  skilled  in  such  matters,  usually  being  somewhat 
wavy  in  outline,  longer  than  broad,  and  with  the  edges  of  the  bark 
slightly  elevated  by  the  escaping  spores.  The  spores  produced  on  the 
white  pine  in  turn  infect  currant  leaves  upon  which  they  may  alight. 
Here  the  period  of  incubation  is  relatively  short,  varying  from  15  to  40 
days. 

On  the  currant  the  fruiting  bodies  appear  at  first  as  tiny  reddish  dots 
on  the  under  surface  of  the  leaves.  Later,  the  fruiting  bodies  form 
small  thread-like  tendrils,  also  on  the  under  surface  of  the  leaf.  These 
spores  may  infect  either  the  currant  or  the  white  pine.     The  spores  pro- 

» Arthur,  J.  C,  North  American  Flora,  vol.  7,  pt.  2,  p.  122.     1907. 
fCir.  38J 


EUROPEAN    CURRANT    BUST   ON    WHITE    PINE.  3 

dueed  on  the  white  pine  can  not  directly  infect  the  white  pine,  but  must 
attack  the  currant.     On  the  currant  the  rust  is  not  known  to  b(   p 
nial,  but  on  the  white  pine  it  remains  alive  as  long  as  the  stem  or  branch 
which  it  int.  - 

FIELD  CHARACTERS  OF  THE  DISEASE. 

The  characters  mentioned  below  apply  only  to  the  disease  in  three- 
year-old   ■  these  are  tie'  only  one-  yet  seen  which  were  affei 

The  affected  tree  has  a  peculiar  stunted  appearance  so  far  as  the  top 
i-  concerned,  while  the  stem  is  swollen  or  enlarged  abnormally.  New 
growth  is  much  shorter  than  on  normal  seedlings,  never  being  over  one- 
halt'  the  normal  length.  The  stem  is  swollen  at  the  int.  cted  place  and 
is  usually  somewhat  spindle  thaped.  In  some  case>  it  is  swollen  along 
the  entire  length  of  the  second  year's  growth,  hut  when  tins  happi 
i-  swollen  irregularly,  the  bark  having  a  bunchy  appearance  in  pla 
A  seedling  with  an  abnormally  thick  Btem  or  one  which  is  irregularly 
thickened  without  any  apparent  injury  to  the  bark  is  diseased.  A  nor- 
mal seedling  will  have  a  stem  winch  is  quite  uniform  in  size  throughout 
each  growth.      Any  injury,  such  as  a  bruise,  will  cause  swelling 

only  at  the  edge  of  the  broken  bark.  Of  course  the  fruiting  bodies  them- 
selves are  the  best  character  by  which  to  recognize  infested  white  pines 
or  currants,  but  on  the  former  they  are  present  only  in  the  spring,  while 
on  the  latter  they  are  present  during  the  late  summer  and  fall. 

There  is  a  native  rust  of  wild  currants  which  is  common  in  some 
sections,  and  this  must  not  be  confused  with  Cronartium  ribicola,  which 
is  entirely  distinct  and  of  different  appearance. 

DAMAGE  CAUSED  BY  THE  RUST. 

The  knowledge  possessed  by  American  pathologists  as  to  the  amount 
of  damage  caused  by  the  rust  is  mostly  based  on  statements  in  Euro- 
pean literature.  On  the  currant  there  is  very  small  damage,  but  this 
is  the  most  dangerous  stage  in  the  life  history  of  the  fungus,  owing  to 
the  possible  infection  of  any  neighboring  white  pines.  On  the  white 
pine  the  damage  is  very  considerahle.  Young  trees  are  killed  outright 
and  small  branches  on  large  trees  are  killed.  In  certain  places  in 
Europe,  notably  in  Holland,  at  Oldenhurg.  Germany,  and  at  Moscow, 
Russia,  this  disease  is  so  serious  that  the  cultivation  of  white  pine  has 
been  abandoned.  In  other  places  the  rust  is  abundant,  and  especially 
in  the  vicinity  of  Hamburg,  Germany. 

METHODS  OF  COMBATING  THE  RUST. 

Very  briefly  stated,  the  practical  method-  of  combating  this  di- 
are  as  follows  : 

(1)  Examine  all  currant  bushes  near  infected  plantations  or  nurseries 
of  white  pine  and  hum  all  that  are  affected;  or,  better,  destroy  all  cur- 

ICir.  38] 


EUROPEAN    CURRANT    RUST    ON    WHITE   PINE. 


Approved : 

James  Wilson, 

Secretary  of  Agriculture. 

Washington,  D.  C,  July  3,  1909. 

O 

[Cir.  38] 


a-  ; 


rants  in  the  vicinity,  if  practicable.     This  should  be  done  from  July  15 
to  the  fall  of  the  currant  leaves. 

(2)  Inspect  imported  white-pine  trees  and  burn  all  that  show  any 
evidence  of  the  disease. 

(3)  Inspect  for  at  least  two  years  all  white  pines  located  near  infected 
currant  bushes  and  burn  all  that  become  infected. 

CAUTION. 

Owing  to  the  peculiar  character  of  this  disease  it  can  not  be  detected 
in  wbite-pine  seedlings  by  any  possible  method  of  dock  inspection 
unless  the  fruiting  bodies  are  present  or  have  been  present.  The  fungus 
lives  for  one  year  in  the  bark  without  giving  external  signs  of  its  pres- 
ence and  can  not  possibly  be  detected  during  this  period.  In  order  to 
have  effective  inspection  of  affected  trees  in  the  field  the  most  expert 
supervision  is  necessary.  Great  care  must  be  taken  that  every  seed- 
ling is  located  and  examined,  all  dead  and  dying  ones  removed  and 
burned,  and  every  suspicious  looking  tree  burned.  Wherever  necessary, 
the  Office  of  Investigations  in  Forest  Pathology  will  give  advice  and 
supervision.  Each  State  is  now  taking  up  the  problem  and  will,  it  is 
hoped,  be  able  to  cope  with  the  situation.  In  view  of  the  great  danger 
from  this  disease  it  seems  best  to  advise  that  no  more  white-pine  seed- 
lings be  imported. 

It  is  believed  that  all  large  recent  importations  of  European  stock 
have  been  located  and  so  can  be  promptby  inspected,  but  it  is  entirely 
probable  that  many  private  importations  have  been  made  which  have 
not  been  located.  It  is  imperative  that  the  presence  of  all  such  stock 
should  be  reported  to  the  State  or  National  authorities,  so  that  prompt 
inspection  can  be  made.  Otherwise  all  efforts  that  are  now  being  made 
to  eradicate  the  disease  may  be  in  vain. 


UNIV.  OF  FL  LIB. 
DOCUMENTS  DEPT. 

":;--  ^.„ 

\ 

U.S.  DEPOSITORY 

i 

